A lot of years.
3 seconds sound clip from the The Train Robbers movie soundboard.
You can hear this line at 00:25:01 in the Blu-ray version of the movie.
Quote context
[...]
- It might mean nothing, but I think I'll take a pass at our back track.
- Jesse?
- How long have you known Lane?
- Me and Grady rode with him during the war. Behind him, I should say. He was our officer.
- We fought together for a couple of years before he ever knew we had a name.
- We've been going up hills together ever since.
[...]